udlfb: Improve debugging printouts with refresh rate

It is not very helpful to print a list of the same resolutions
without the refresh rate.

Signed-off-by: Bernie Thompson <bernie@plugable.com>
diff --git a/drivers/video/udlfb.c b/drivers/video/udlfb.c
index a40c05e..04aea20 100644
--- a/drivers/video/udlfb.c
+++ b/drivers/video/udlfb.c
@@ -1012,7 +1012,8 @@
 		return 0;
 	}
 
-	pr_info("%dx%d valid mode\n", mode->xres, mode->yres);
+	pr_info("%dx%d @ %d Hz valid mode\n", mode->xres, mode->yres,
+		mode->refresh);
 
 	return 1;
 }